Can you store flash cotton and flash string inside a glass jar with a sealed lid or does it have to have some air?

How long does it last before it doesn't work anymore? Can it go years?

I've had flash paper stored in a metal tin for a couple years and it still worked albeit the burn was a little slower. I've also had it stored in a sealed bag and it went off.

I have been told that storing it in the freezer will extend it's life considerably.

I had some flash paper store in a zip lock bag... Forgetting it was in this drawer.. And when I went to use it and took it out it crumbled in my hand.. SO it certainly doesn't last forever.. SO I don't know what happened to mine

I have heard to store it in the freezer. Does it work, not sure, never tried.....